Musical-instrument loud-speaker



Jan. 28, 1930. I A. MQL. NICOLSON 1,744,916

MUSICAL INSTRUMENT LOUD SPEAKER I Filed April 15, 1927 Fig. 5

. INVENTOR ALEXANDER MCLEAN NICOLSON BY w Patented Jan. 28, 1930 UNITED STATES PATENT OFFICE ALEXANDER MGLEAN NIOOLSON, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGN- MENTS, T FEDERAL TELEGRAPH COMPANY, A CORPORATION OF CALIFORNIA MUSICAL-INSTRUMENT LOUD-SFEAKER Application filed April 13,

, This invention relates to sound reproducing apparatus and more particularly to such apparatus known as loud speakers, and adapted to reproduce sounds from electrical oscillations corresponding thereto.

It is an object of this invention to provide improved apparatus of the class described, utilizing a series of resonant vibrating bodies each having one or more different natural I frequencies of vibration, and a sounding board arranged to sustain and amplify the vibrations of such bodies, together with apparatus particularly adapted to cause vibration of such bodies and which will preferably although not necessarily, be in the form of one or more piezo-electriccrystal devices arranged in a manner which I have found most effective. a

It is a further object of this invention to zoprovidea vibrating or driving apparatus in the form of a unit which may be easily and quickly attached to a musical instrument having a sounding board and a plurality of vibrating elements of different natural frequency, such for example as a piano, without making any alterations or changes in the instrument and particularly without the necessity of drilling or cutting into the sounding board.

Still other objects of my invention will be apparent from'the specification.

The features of novelty which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its fundamental principles and as to its practical application will best be understood by reference to the specification and accompanying drawings, in which:

Fig. 1 illustrates one form of my invention as embodied upon a harp.

Fig. 2 illustrates a different form of my invention, as applied to a Violin.

Fig. 3 is a top plan view of still another form of my invention showing my apparatus permanently secured in place upon a piano.

Fig. 4 is a detail view partly 111 section'of the apparatus shown in Fig. 3; and

Fig.'5 is a plan view of still another form 50 of my invention showing its adaption to a 1927. Serial No. 183,345.

piano in a manner requiring no drilling or cutting of any part of the piano.

In accordance with my invention I provide apparatus utilizing a sounding board having a preferably aperiodic characteristic and having associated with" it a plurality of.

resonant vibrating bodies of different natural frequencies covering the band of frequencies which it is desired to reproduce. Musical instruments of the string and sounding board type, such as the harp, violin, piano, and the like, lend themelves particularly to my invention. I utilize a driving means which may, for example, and preferably will be one or more piezo-electric crystal devices adapted and arranged to be vibrated by electrical oscillations corresponding to the sounds to be reproduced. However, it will be understood that my invention is not limited thereto and that other driving apparatus may be be employed, if desired.

I preferably secure the driving apparatus to the sounding board of the musical instrument in such manner that the sounding board is directly driven and the vibrations thereby communicated to the strings, although this is not essential, and I may connect the driving apparatus to some other part of the instrument or even to one or more of the strings, if desired. a In cases Where it is not objectionable to drill or cut the sounding board of the instrument, I may bolt or otherwise permanently secure the driving means to the sounding board in such manner that the sounding board is set into vibration by vibrations of the driving mechanism.

In cases Where it is undesirable to mutilate the sounding board, I may provide driving surface against the sounding board.

A 20 1926, or if des' impedance 1 '4 and 5 adapted to carry the weight of the harp.

The driving means may be in the form of a pair of PlGZO-GlGCQ-lc crystal devices 7 and 8, which may, for example, be Rochelle salt crystals exhibiting; the well known hour glass configuration, drilled internally for bolt 9, by means of which they are secured to base 3 provided with an opening 10 to adinit the head of the bolt 9. lhe crystals may be secured together in addition by means of Rochelle salt melt comprising Rochelle salt from which a suitable amount of water has been removed by heating the same at a ternperature above its melting point. A second set of crystals 11 and i2 is similarly arranged to be secured by bolt 13, and a suitable stress plate of elastic metal such as steel is held in position at the top of the crystals 8 and 12,

pposite ends of the stress plate 14- are secured to suitable points upon the sounding board 1 as by bolting, and suitable metal hearing washers l5 and 16 are interposed to provide a relatively large stress transmitting; Suitable sound absorbing Ina ca as felt or leather will be preferably inter-pose l between any metal to metal. joints to prevent rattle which night otherwise occur.

The crystals are pref ly provided with a air of electrodes eac 18 is, 20, 21 22 23, 2 l trical oscillations Y cm stal device-s.

n oi these el 1115 invention,

i lay be utilised: preieracly i may constitute an internal e ectrode each Jr 1. 4* *3, ,1 o tae crystals '2 and 8 iii; the otnei elect each may be equatoriai conuuctingi such as incel ion. apulieu may be COIIRGCEQd 1 leads and 26, which source of electric soi rangenients oi Ci and, such as those described and inycopending applications e posits piezoelec ric torsion \C vice, i No; 155,399, file i1, iii-1 inter-nail clamped .con posits piezoelectric torsion de vice, Serial l lo 155 905 tiled 20, 192 and Orient if component crystal in composite pie o-electric devices filed Dec electric-static driving In tl is connection since the internal 'not' piezoelectric crystal nigh in order to obteirl a l 1 Sci plate 1 1 is connected on the sounding board ing means Li Willa s used, the

s provi sounding board will be correspondingly modified.

Referring now more particularly to Fig. 2, I have shown my invention as applied to a violin. In this instance, there is provided a base 6 suitably arranged to support a violin 29, and the base 6 may be provided with an extension 6 upon which is mounted a suitable driving means such as piezoelectric crystal device 27 having a suitable stress plate 28 se cured thereto to which is attached a driving rod 30 suitably secured to the sounding board of the violin as by means of a bearing plate 31. The crystal device 27 is provided with a pair of electrodes 82 and 33 which may be arranged in the same manner as described fon Fig 1.

Referring now more particularly to Figs. 3 and a, I have shown my invention as en1- bodied upon a piano having a frame 42 supporting a sounding board 41 protected by a covering plate 43 having a series of openings therein. As this construction is the conventional piano construction, I do not believe it necessary to describe it in detail. A suitable driving means is provided such for example as piezoelectric crystal device which may be in the form of a crystal of Rochelle salt as above described provided with stress plates 56 and 5'? secured thereto at opposite basal planes themed and extending latera ly on opposi e sides oi the crystal. The plates may be canented to the crystal addition a bolt 58 w)? more pa ticularl i nay be provided projecting extension 60 and stress plate 57 a similar eXtei-ision 6L netal plate 63 of relatively large sur 1S interposed n ed the sounding board ll and. a suitable h *le therwasher positio ed betwen eater 60 and bear- -ding to beer and her an 1 the whole is secured in position by means nut engaging bolt 6'? passing though stress'plate 56, washers 62 nd bearing plates 63 65 and the sounoi board 41-1. A similar construction 1 reference to extension ("31 of stress plate 5?, the hearing plates being designated as 69 and 70, and ti e washers as 68 and '71: nut '72 b Y3 to secure these members in position. Electrical oscillations may be supplied. to the crystal by suitable electrodes 74 and 7t before Under certain conditions, it may be clesirable to leave the sounding board of the musical instrument intact. For the purpose I securing the benefits of my invention unsuch conditions I mar? provide carasuch as shown in Fig in which the vi be in the is provided 1 the audible range, and by the use of such.

with stress plates 45 and 46 suitably secured thereto as by cementing and bolting, by means of bolts 47 and 48. Suitable bearing plates 49 and 50 may be secured to the stress plates 46 and 45 respectively, and may be secured thereto by being bolted or Welded to the stress plates 45 and 46; and electrodes 51 and 52 of a suitable type such as already described, may be provided for the purpose of impressing electrical oscillations upon the crystal devices. The assembly may then be weighted by means of a lump of metal so as to be relatively ponderous, and will then be placed upon the sounding board of the piano, as may be found'to produce the best results: when oscillations are. supplied to the electrodes, stresses are developed by the crystal in accordance therewith, which stresses are transmitted through stress plates 45 and 46 to bearing plates 49 and 50v and thence to the sounding board of the piano.

It will be noted thatsince a piano comprises a set of strings tuned to a large range of fundamental frequencies and since each of the strings responds to a number of harmonics or overtones, which are different in the case of each string, the sounding board and its strings comprises an acoustic vibrator having an element having a natural resonant frequency of practically any frequency'within apparatus, it is possible to provide speech and music reproduction of considerable volume and of very excellent quality, without recourse to excessive power, as will be the case when non-resonant devices are utilized.

It will be understood that While I have shown and described the use of piezo-electric crystals for driving the sound reproducing apparatus, other means such as electro-magnetic or electro-static driving units may be utilized, and it will also be understood that while I have described my invention as a sound reproducer adapted to reproduce sound from electrical oscillations, that such apparatus is electrically reversible and may produce electrical oscillations from sound vibrations.

While I have shown and described certain preferred-embodiments of my invention, it

will be understood that modifications and changes may be made as will be understood by those skilled, in the art, without departing from the spirit and scope of my invention.

1. A loud speaker comprising a piezo electric crystal device, a pair of-stress plates con- 5 with each end of said device, each stress plate tacting with opposite ends of said device, and bolt members extending through said stress plates for connecting to a sounding board of a stringed musical instrument for causlng vibrationsof said strings and said sounding board at sound frequencies.

2. A loud speaker comprising a piezo electric crystal device, stress plates contacting the sounding board of a stringed musical instrument for causing vibration of said strings and said sounding board at sound frequencies.

3. A loud speaker comprising a piezo electric crystal device, stress plates each having a vertically extending supporting portion and a laterally extending portion, the contacting portion of each stress plate abutting with one terminal of said device, said supporting portion being secured to the sounding board of'a stringed musical instrument for causing vibration of said strings and said'sounding board at sound frequencies.

4. A loud speaker comprising a piezo electric crystal device, a pair of right angularly disposed metallic members having portions thereof directed toward each other and secured to said piezo electric crystal device and having other portions secured to a sounding board adjacent a nodal point thereof said piezo electric crystal device being rigidly secured to said right angularly disposed members for transmitting sound vibrations to said sounding board.

5. A loud speaker comprising a piezo electric crystal device comprising a plurality of piezo electric crystals, a stress plate contacting with each end of said device, a projection on each stress plate receiving a bolt member for rigidly securing said plate in position upon the sounding board of a stringed musical instrument to vibrate said strings and said sounding board at sound frequencies in accordance with sound frequency modulated energy fed to said piezo electric crystal device.

6. A loud speaker comprising a piano having a plurality of tensioned strings and a sounding board, a piezo electric crystal device, a pair of massive stress plates secured to said crystal, and connections between opposite terminals of said piezo electric crystal device and said sounding board fortransmitting stresses from said stress plates to said sounding board and said strings at sound frequencies in accordance with modulated energy fed to said piezo electric crystal device.

Signed at New York, in the county of New York and State of New York, this 12th day of April A. D. 1927.

ALEXANDER MoLEAN NICOLSON. 

